"This insulator replaced the old Compromise
insulator which was an accepted telegraph standard. Probably ten million compromise
insulators were in service in the years 1865-1881."

"By 1881, glass-making had progressed to a point where an economical double
petticoat was possible, and the Hemingray No. 21 was the result. This insulator, also known
as the "Standard DP" or "Western Union Standard" was widely used down to
about 1900 and still is in limited use."

Common Variations:

Colors:

Hemingray Blue, Aqua, and Clear

Bases:

Smooth, Round or Sharp drip points

Embossings:

(F-Skirt) HEMINGRAY (R-Skirt) No
21
(F-Skirt) HEMINGRAY/MADE IN U.S.A. (R-Skirt) No
21
(F-Skirt) HEMINGRAY-21 (R-Skirt) MADE IN
U.S.A.(Numbers and dots may appear below the embossing on either or both the front
and the back)
If your insulator has "numbers and dots" on it, you can find out
more about them
by reading this information about dating
your insulator.